Question 237: AC fundamentals

Question

A resistor $$'R'$$ and $$2\mu F$$ capacitor in series is connected through a switch to $$200$$ $$V$$ direct supply. Across the capacitor is a neon bulb that lights up at $$120$$ $$V.$$ Calculate the value of $$R$$ to make the bulb light up $$5$$ $$s$$ after the switch has been closed. $$\left( {{{\log }_{10}}2.5 = 0.4} \right)$$

Accepted Answer

We have, $$V = {V_0}\left( {1 - {e^{ - t/RC}}} ight)$$
$$ \Rightarrow 120 - 200\left( {1 - {e^{ - t/RC}}} ight)$$
$$ \Rightarrow t = RC\,in\,\left( {2.5} ight)$$
$$ \Rightarrow R = 2.71 	imes {10^6}\Omega $$

Answer

$$1.7 	imes {10^5}\,\Omega $$

Answer

$$2.7 	imes {10^6}\,\Omega $$

Answer

$$3.3 	imes {10^7}\,\Omega $$

Answer

$$1.3 	imes {10^4}\,\Omega $$

AC fundamentals

A resistor $'R' and 2\mu F capacitor in series is connected through a switch to 200 V direct supply. Across the capacitor is a neon bulb that lights up at 120 V. Calculate the value of R to make the bulb light up 5 s after the switch has been closed. \left( {{{\log }_{10}}2.5 = 0.4} \right)

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